Adrenal Insufficiency for PA
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Adrenal Insufficiency for the Physician Assistant Licensing Exam
- Pathophysiology
- Primary Adrenal Insufficiency (Addison's Disease): Occurs due to destruction of the adrenal cortex, leading to deficient cortisol, aldosterone, and androgen production. This causes hypotension, hyponatremia, and hyperkalemia due to aldosterone deficiency, along with hypoglycemia and fatigue due to cortisol deficiency.
- Secondary Adrenal Insufficiency: Results from insufficient secretion of adrenocorticotropic hormone (ACTH) by the pituitary, leading to low cortisol levels but preserved aldosterone secretion.
- Tertiary Adrenal Insufficiency: Caused by impaired corticotropin-releasing hormone (CRH) secretion from the hypothalamus, usually due to chronic glucocorticoid use, which suppresses the hypothalamic-pituitary-adrenal (HPA) axis.
- Etiology
- Primary Adrenal Insufficiency:
- Autoimmune Destruction: The most common cause in developed countries.
- Infections: Tuberculosis and fungal infections (e.g., histoplasmosis) can damage the adrenal glands.
- Adrenal Hemorrhage: Seen in Waterhouse-Friderichsen syndrome, often due to meningococcal sepsis.
- Secondary/Tertiary Adrenal Insufficiency:
- Chronic Glucocorticoid Use: Suppresses ACTH and CRH, leading to adrenal atrophy.
- Pituitary Tumors or Surgery: Causes ACTH deficiency.
- Clinical Features
- Primary Adrenal Insufficiency:
- Fatigue, Weakness, Anorexia: Due to cortisol deficiency.
- Hypotension: From both cortisol and aldosterone deficiencies.
- Hyperpigmentation: Increased ACTH stimulates melanocytes.
- Hyponatremia and Hyperkalemia: Due to aldosterone deficiency.
- Secondary/Tertiary Adrenal Insufficiency: Similar symptoms, but without hyperpigmentation or significant electrolyte disturbances.
- Diagnosis
- Morning Cortisol: Low levels (<5 µg/dL) suggest adrenal insufficiency.
- ACTH Stimulation Test: Used to differentiate between primary and secondary causes.
- Electrolytes: Hyponatremia and hyperkalemia in primary adrenal insufficiency.
- Treatment
- Primary Adrenal Insufficiency: Requires glucocorticoid (hydrocortisone) and mineralocorticoid (fludrocortisone) replacement.
- Secondary/Tertiary Adrenal Insufficiency: Glucocorticoid replacement only.
- Acute Adrenal Crisis: Managed with IV hydrocortisone and fluid resuscitation.
Key Points
- Pathophysiology: Primary adrenal insufficiency affects both cortisol and aldosterone, while secondary and tertiary forms affect cortisol only.
- Etiology: Primary causes include autoimmune destruction, infections, and adrenal hemorrhage, while secondary/tertiary causes are often due to chronic glucocorticoid use.
- Clinical Features: Primary adrenal insufficiency presents with fatigue, hypotension, hyperpigmentation, and electrolyte disturbances.
- Diagnosis: Low morning cortisol, ACTH stimulation test, and abnormal electrolytes in primary adrenal insufficiency.
- Treatment: Glucocorticoid and mineralocorticoid replacement in primary disease, glucocorticoid only in secondary/tertiary disease.